yep someone made a rocket launcher you contol with your pc...  its range is 360 degree horizontal rotation and 45 degree vertical rotation, the USB Rocket Launcher can fire over six meters... imagine  converting this into a REAL weapon.. it could be done... make a sentry bot lol

buy it here
http://www.thinkgeek.com/geektoys/warfare/8a0f/

-edit-
theres more of an arsenal then i thought lol heres two more
this is what i want


Includes: USB MSN Missile Launcher, 3 Foam Darts, Target, Software, Instructions
Features:
Aim and fire at targets using the built-in webcam and MSN Messenger.
Take control over your buddy's missile launcher and shoot them!
Missile Launcher can pan left and right and tilt up and down.
Sound effects (from your computer) when you launch your buddy's missiles.
Can also be used as just a webcam.
USB Cord Length: 3 feet
Range: 15 feet
Software Compatibility: Windows XP/2000/Vista

Where would wee be without Instant Messaging? It lets us stay in contact and chat with friends all over the world (especially delightful during work hours). But sometimes the urge to reach out a shoot someone is unbearable. And that's where the USB MSN Missile Launcher comes in. Don't be content with sharing images, jokes, and assorted links with your friends - it's time to share missiles!

You'll have your USB MSN Missile Launcher set up within minutes and that's when the fun begins. For you see, as you chat you and your buddies can control each other's launcher. And since each USB MSN Missile Launcher has an integrated webcam (which can be used as just a webcam if you haven't any buddies), you'll know exactly when you are aimed at your buddy's head. Then fire away! The only downside is that your buddy can do the same to you! The upside is, you can always retaliate by turning your buddy's USM MSN Missile Launcher to face the door of his office and peg his boss in the gut when he/she comes to lecture your buddy about using IM for non-work-related matters. Ah the joys of progress . . . and revenge.

http://www.thinkgeek.com/geektoys/warfare/a1c2/

and a missle launcher!!


With the ability to connect (and simultaneously control) an almost unlimited number of missile launchers (well, only limited by your system memory and number of USB ports), the USB Laser Guided Missile Launcher will empower you to unleash something akin to total office annihilation. Not only will you achieve strength with the size of your battery of missiles, they will be accurate too. The built-in laser missile aiming system will allow you to aim and fire your weapons with close to pinpoint accuracy! Just point the red laser dot at your target and slowly squeeze your mouse trigger finger. However, should you choose to opt for a stealth ambush, the laser can also be easily turned off.
http://www.thinkgeek.com/geektoys/warfare/8bc4/

i want one!!!

ill get one and black tape a pen laser and a web cam to it and have a sentry with eyes and a sight lol that would be awesome... just set in in the corner of my house somewhere and start attacking my friends

check the first post again lol

or what about a marshmellow gun

These have been out for ever.